Portland State University. Department of Mechanical and Materials Engineering
Mark M. Weislogel
Date of Publication
Master of Science (M.S.) in Mechanical Engineering
Mechanical and Materials Engineering
Film boiling, Drops, Reduced gravity environments, Hydrophobic surfaces, Fluid mechanics -- Research
1 online resource (xix, 124 pages)
Leidenfrost phenomenon has been studied extensively for its role in applications ranging from nuclear reactor cooling, to metals manufacturing, combustion, and other fields. Herein, Leidenfrost phenomenon is pursued towards non-contact distillation processes with hopes of reducing or even eliminating contaminant fouling. In particular, the microgravity environment of a drop tower is exploited to demonstrate the facility with which droplets achieve and sustain the Leidenfrost state. Dynamic Leidenfrost impacts in microgravity are presented for impacts on hydrophilic and superhydrophobic planar substrates, macro-pillar arrays, confined passageways, and others. Nearly ideal elastic non-contact impacts and droplet oscillation modes are observed. Dynamic Leidenfrost impacts in microgravity for uniquely low velocity impacts are investigated analytically and experimentally. We find Leidenfrost vapor layer thicknesses on the order of millimeters for a 1 mL droplet of water with impact velocity 1 mm/s - a 100-fold increase relative to terrestrial vapor layers. Such results are supported by preliminary experimental observations. Further droplet distillation experiments are conducted in a terrestrial gravity environment using a heated tilted rotating hemi-circular track. Droplet evaporation rates and lifetimes are tabulated for the sliding/rolling drops at varying angular velocities and tilt angles. An analytical model for the evaporation rate of a rolling Leidenfrost droplet is developed and compared to the experimental results with good agreement. The empirical and analytical results serve as key design tools for sizing a prototypical non-contact distillation system for terrestrial desalinization or spacecraft water recycling.
Rasheed, Rawand Muzafar, "Non-Contact Distillation" (2019). Dissertations and Theses. Paper 5275.